北部湾盆地福山凹陷构造转换带对层序及沉积体系的控制

Control of transfer zone over sequences and depositional system in Fushan sag,Beibuwan Basin

基于福山凹陷典型三维地震解释结果,以流沙港组构造转换带为研究对象,对其层序构成样式和沉积体系展布特征进行研究。结果表明:构造转换带发育于凹陷中部花场地区,并起到调节东西部构造差异性的作用,其两侧所发育的层序构成样式差异显著,西部发育多级断阶型层序样式,东部发育缓坡型层序样式;构造转换带处发育挠曲坡折型层序样式,高位域时期发育大规模辫状河三角洲沉积体系,低位时期发育大范围浊积扇;福山凹陷的沉积充填演化受到构造转换带、相对湖平面变化和古地貌联合控制,不同体系域内转换带对沉积充填控制作用也有一定的差异性。

Based on the interpretation of the 3D seismic data, the sequence patterns and sedimentary characteristics in the sedimentary period of Liushagang formation were studied taking the transfer zone of the Fushan sag as the research project. The results show that the transfer zone developing above the Huachang in the centre of Fushan sag, plays a crucial role in ad- justing the structure differences between the western and eastern areas. There are significant differences on the strike of faults and structure styles between two extensional structure systems, which develops at two lateral sides of the transfer zone respec- tively. The multi-level step-fault belt type of sequence pattern develops in the western area, while the gentle slope type of se- quence pattern in the eastern area. The flexure slope break type of sequence pattern develops in the transfer zone with huge- scale braided channel delta in the high system tract and large-scale turbidite fan in the low system tract. Structural transfer zone, relative lake level changes and paleogeomorphy control the sequence architecture and depositional filling of the Fushan sag together, and this controlling effect varies among different system tracts to some extent.